Method of preparing halobutadienes



Patented 1936 UNITED STATES PATENT orric-n' I METHOD PREPARING HALO- BUTADIENES Wallace H. Carothers, Fairville Pa., assignor to E. I. du Pont deNemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application November 2, 1931,

7 Serial No. 572,723

, -9.Ciaims. (Cl; 260-165) This invention relates to a process forpreparing halogen-substituted butadienes. more specifically to the preparation of chloro- 2- butadiene-1,3 from,dichlro-3A-butene- 1.

Chloro-2 -butadi ene-1;3 was first described in a copending application of Carothers and Collins,

Serial No. 490,538, filed October 22, 1,930,, who,

showed that this compound can be obtained by They showed further in 'Carothe rs and the addition ofhydrogen chloride tofvinyl acetylene.

Collins, Serial, No. 519,243, filed February. 28, 1931 that chloro-2-butadiene-1,3 is capable of be-- ing polymerized to. rubber-like products and.

dichlorides, namely, dichloro 3,4 butene '1, CHgCl-CHCICH=CH2, and dichloro-1,4-bupounds can be separated from the chlorination product of butadiene by fractional distillation. Muskat and Nort dichloro'-1,4- butene-2 is treated with caustic alkali it loses hydrogen chloride ;with'- the formation of chloro-l-butadiene-l}, I

CICH=CH CH=CHa They state further that thesame compound'isl obtained by the action of caustic alkali -on.dl-

chloro-3,4-butene-1. 1 They describe chloro-l-w butadiene-.l,3 as a colorless liquid which boils at 85 C. under atmospheric pressure and ,poly- .35

merizes on standing to a. dark resinous mass.

a method for the preparation of chloro-2-butadiene-1,3 which does not involve the use or vinylacetylene as afstarting material.

40 Other objects willappear fromga study or the following'description of the invention.

I have found that chloro-2-butadiene-1,3 can be prepared very easily by treating dlchloro-3,4- butene-l with caustic alkali or with another agent 45 capable of neutralizing hydrochloric acid. The reaction consists in the elimination of hydrogen chloride and proceeds in accordance with the 'following equation: v cmc1 cHc1 cH=cn='- cm= I v v CHCI.C I- I=CH2+H I As already mentioned, it has been stated. by Muskat and Northrup that chloro-l butadiene- 1,3 is formed in this reaction.

It relates ,count the properties indicated above.

', catechol.

up have alleged-that when An object of the present invention-is to provide I have found, how'- .55 ever, that chloro-2-butadiene-l,-3 is the principal product of the reaction; However, in order to actually isolate chloro'-2-butadiene-1,3 from the diminished pressure and/or in the presence of a C polymerization inhibitor such as pyrogallol' or The preparation of chloro-2-butadime-1,3 by this process is illustrated in the i01 lowing examples: 4

I Example I I One hundred and six g. of dichlor'o-3,4 butene- '1 and 210g. of solid potassium hydroxide "are mixed in a 500 cc. distilling flask provided with a Liebig condenser. The flask is heated by means of a water bath. At a temperature oi' about 95- C. a-vigorous reaction sets in and chl0ro-2-buta .25 -diene-1,3 rapidly distllls into the receiver at- .tached'to'the condenser. When the vigor of the reaction has somewhat abated theflask' is gently heated with a free flame to drive all of the chlorobutadiene into the receiver. The crude reaction product amounts t6 about 62 g. 'It consists essentially of-chloro-2-butadiene-L3 contaminated with some unchanged fdichloro-3,4-butene-1. It may be purifiedby distillation. In this process of distillation it is preferable to mix with the prodnot a small amount of a polymerization inhibitor such as pyrogallol or catechol and if the amount of material'to-be distilled is large (e." g., more than 150. 3.) it is preferable to carry out the distilla'tior "in vacuo. The ohloro-2-butadiene-l,3

trlbuted. to' chloro2-but adiene-1,3'by Car'others and Collins in the copending application Serial. No. 490,538, filed October 22, 1930, referred to above, now United States Patent #1,950,431.

'I'he dichloro-3,4-butene'-l required for this reaction can be conveniently prepared by the fractional chlorination ,oi' buta v tillation Or -any other suitable-method .may be ene followed by. disused. -It is t'oibe understood that the above-example isiillustrative only and the experimental condi-I Other alkalies may be used in place of the po-' ta'ssium hydroxide such as sodium hydroxide, calcium hydroxide,- calcium oxide, soda lime, etc. It is possible also to remove hvdrogen chloride from dichloro-BA-butene-l by heating it with organic bases such as dimethyl aniline, pyridine, or quinoline. In carrying out the process dilu-q ents such as liquid organic solvents may be present if desired.

nection with the preparation of chlorobutadienes. It is also applicableto the preparation oi! other halogen-substituted butadienes, e. g., bromobutadienes, having analogous molecular structure.

The above description or the invention is illustrative only. It is to be understood that any modification or departure from the details of invention outlined above which conforms to the principle of the invention, is intended to be ini cludedwithin the scope of the claims.

I claim: 4 1. The process of preparing chloro-2-buta- 'diene-1,3 which comprises reacting dichloro-3,4- butene-l with anagent which will remove one molecule of hydrogen chloride, subjecting the reaction product to fractional distillation andseparating in substantially pure form a product boiling at substantially C.

2. The process described in claim 1 in which thesaid agent is alkaline in character.

3. The process described in claim 1, in which 7 the said agent is caustic alkali.

4. The process of preparing chloro-2-butadime-71,3 which comprises reacting dichloro-3,4-

aoaassa butane-1 with an agent which will remove one molecule of hydrogen chloride, formed chloro'-2-butadi'ene-1,3 by fractional distillation and obtaining the same in a substantially pure state, the distillation being carried out in the presence 01 a polymerization inhibitor in order to prevent spontaneous polymerization of the chloro-2-butadiene-1,3.

5. The process of preparing chloro-2-buta- (hone-1,3 which comprises reacting dichloro-3,4'- butene-l with an agent which will remove one molecule of hydrogen chloride, removing the formed chloro-2-butadiene-1,3 by fractional distillation and obtaining the same in tially pure state, the distillation being carried out under reduced pressure in order to prevent The above process has been described in conspontaneous polymerization of the chloro-Z-butadiene-1,3.

6. The process of preparing chloro-2-butadime-1,3 which comprises reacting dichloro-3,4-

butene-l with an agent which will remove one molecule ofhydrogen chloride, removing the formed chloro-2-butadiene-1,3 by fractional distillation-and obtaining the same in a substantially pure state, the distillation being carried out under conditions which will inhibit polymerization of the chloro-2- butadiene-1,3.

. 7. The process of preparing halogen-2-butadime-1,3 whichcomprises reacting a dihalogeni 3,4-butene-1 withhan agent which will remove one molecule of hydrogen halide, then separating the halogen-2-butadiene-L3 in a substantially pure state by fractional distillation.

8. The process of claim '1 characterized in that the said agent is alkaline in character.

9. Theprocess oi claim-'7 characterized in that the said agent is caustic alkali and the distillation is carried outunder conditions which inhibit the polymerization of the halogen-2-butadiene-L3. 40

WALLACE H. CAROTHERS.- 

